Apparatus for and method of operating dynamo-electric machines



July7,1925. 1,544,780

H. SHOEMAKER ET AL APPARATUS Fm AND METHOD OF OPERATING DYNAMO ELECTRIC MACHINES Filed Aug. 1919 2 Sheets-Sheet QOOOOO N I X k July 7, 1925. 1,544,780

H. SHOEMAKER ET AL APPARATUS FOR AND METHOD OF OPERATING DYNAMO ELECTRIC MACHINES Filed Aug. 27, 1919" 2 Sheets-Sheet 2 t 71%7/5 57 H v I I Patented July 7, 1925.

UNITED STATES 1,544,780 PATENT. OFFICE.

HARRY SHOEMAKER, OF JERSEY CITY. NEW JERSEY, AND CLIFFORD D, MALLORY,

OF GREENWICH, CONNECTICUT, ASSIGNORS, BY DIRECT AND MESNE ASSIGN- MENTS, TO'MALLORY DIESEL ELECTRIC CORPORATION, A CORPORATION OF DELA- WARE.

x APPARATUS FOR AND METHOD OF OPERATING DYNAMO-ELECTRIC MACHINES.

Application filed August 27, 1919. Serial No. 320,141.

T 0 all whom it may concern:

Be it known that we, HARRY SHOE AKER and CLIFFORD D. MALLORY, citizens of the United States, residing at Jersey City, New Jersey, and Greenwich, Connecticut, respectively, have invented certain new and useful Improvements in Apparatus for and Methods of Operating Dynamo- Electric Machines, of which the following 1s a clear, full, and exact description.

This invention relates to apparatus for and method of operating and controlling dynamo electric machines, and a general object of the invention is to provlde a construction which will be more flexible and economical than those heretofore in use.

More particularly the invention relates to means for efi'ectively utilizing the power of certain types of prime movers under conditions requiring both flexibility and range of power, as, for example, in the propulsion of ships. Although the invention is herein shown as embodied in means for generating and applying power for ship propulsion, it will be understood that the invention 1s not restricted to the illustrated embodiment and uses and that the invention, in many of its aspects, is of'general utility in the dynamo electric machine art.

In ship propulsion it is important that the propelling means use up as little cargo space as possible, both with respect to the space required for the installation of the mechanism itself and with respect to the space required to store fuel sufficient for the ships voyage. Moreover, in V ew of the increasing labor costs and the requirements of the navigation laws it is also important that the number of members of the crew required to look after the propelling mechanism be reduced to a minimum. Steam pro- -pulsionis extravagant both in space and in ,.the number of men required to look after the boilers and engines, and although some space saving has been effected by the introduction of steam turbines and 011 burners, nevertheless, the crew requirements for steam propulsion are still large, and also the space requirements. Electric transmission has been utilized with, Diesel engines in submarines and other types of warships, but the installations have been too complicated and have required too much highly skilled attention to warrant their use m commercial ships in competition with other means of ship propulsion,

A particular object of the present inventron, therefore, is to provide means for ship propulsion which will make available all of the space saving advantages of internal combustion motors, such, for example, as the Diesel engine, and the space saving advantages and flexibility of operation of electrical transmission; which will moreover be so slmple in its operation and control as not to require particular skill in the attendants andwhich furthermore is so constructed and arranged as not to be liable to the interruptions in operation which have heretofore characterized ship propulsion by internal combustion motors.

An' important feature of the invention is the utilization, of a plurality of internal combustion motors so constructed and arranged with respect to the electrical transmission that any or all of the prime movers and of the associated generators may be operated in connection with any or all of the elements of the motormechanism. A further important feature is an arrangement of electrical control of the power transmission mechanism such that current losses through resistance are avoided and that the weight and space requirements of the elec-' trical units are reduced to the minimum. Still further important features of the invention are the fool-proof interlocking of the control of the electrical transmission; the novel winding of the generator fields whereby the field strength may be varied without the use of resistance and whereby also economy is effected in the size of the wire required for the field winding; the novel means for insuring stopping of the propelling motor mechanism and for insuring proper electrical conditions in the whole transmission mechanism before reversal of the propeller; the novel arrangement for starting the main prime movers and for exciting and for controlling the excitation of the generator and motor fields; and, in general, the simplicity, compactness, lightness and efliciency of the electrical wiring and of the ho e e ct ical transmission mechanism.

Other important features and objects of the invention will be apparent. from thefollowin description:

In 51c drawings showing the embodiment of our invention which we now prefer, Fig. 1 is a dagrammatic v1ew;

Fig. 2 a detail of connectlons;

Figs. 3, 4 and 5-other details, the latter showlng a modification of generator field control which may be used if desired,

In the above preferred embodiment, referring particularly to 1, we have provided a plurality of maln operat ng units having independently operating prime movers such as the internal combustion engines 1 and 2. Directly connected to each prime mover is a generator 3 or 4, the armatures of which supply current to a suitable dynamo electric motor mechanism which, 1n the present embodiment is represented as a pair of motors 5 and 6 mounted on the same shaft and shown as driving a load, such as a shlps propeller 7. The armatures of the generators are preferably normally connected in series, as indicated, and supply current to the armatures of the motors 5 and 6. The

latter are shown as connected in series, but

such connection is not necessary in all cases. Suitable switches, indicated as a whole by A and B, are provided by which other connections may be made if desired.

The generators are preferably separately excited, that is, preferably exc ted bya current generated by some outside source of E. M. F. In the present embodiment of our invention, we have shown as such exclt ng source exciters 8 and 9 driven by the prime movers, and preferably directly connected to the corresponding generators 3 and These exciters may be compgund wound, if desired, and have been so shown, although they may be wound otherwise if desired. Rheostats 10 and 11 may be provided for varying their field excitation.

Each exciter preferably excites the field of its own generator. Referring to exciter 8, for example, from its brush 12 the circult may be traced to the, point 13 and from there to switch 14 to the point 15, from there through the field coil 16 of generator 3 and by wire 17 to 'a controller later to be described, and back by wire 18 through switch, 19' to the other brush.

The dynamo electric motor mechanism generically represented by 5, 6, preferably has a plurality of field windings. Fig. 1 represents two complete motors comprising the motor mechanism but in the diagrammatic Fig. 2, we have represented only one armature 27 but provided with two fields 21 and 24. Obviously it is, broadly speaking, immaterial what type of motor mechanism is used, but at present we prefer one of the two types illustrated. If a construc tion is used which is provided with two independent fields, we prefer that one field normally shall be energized by one exciter and the otherby the other exciter, and have so shown it. In Fig. 1, for example, starting from the point 13, the circuit may be traced to the point 19. switch 20, through field 21 and back through switch 22 to the other terminal of exciter 8.

Similarly, exciter 9 energizes the field 23 of generator 4 and also excites the field 24 of the motor mechanism.

The connections in their normal running condltlon may be more clearly seen from Fig. 2, in which the parts are similarly numbered. In this dia ram, although two inde-.

pendent motor-fiel windings are shown, the armature windings are all connected to one set of brushes, instead of having the windings split into two parts with two sets of brushes, as shown in Fig. 1. Either construction may be used.

As shown in Fig. 2, which also may be taken as a more simple diagrammatic representation of Fig. 1 in its running condition, the two generator armatures 25 and 26 are connected in series, and, through a reversing switch C, are connected to the armature windings 27 of the motor mechanism. The exciters 8 and 9 ener ize the fields of the generators and the fie ds 21 and 24 of the motor mechanism. We prefer normally to give a substantially constant excitation to .the field or fields of the motor mechanism and control the speed of the motor by varying the field strengths of the generators, thereby obtaining great starting torque for the motor and flexibility of running condition. We preferably do this by arranging the motor and generator fields in parallel from the exciter or exciters and suitably controlling the output of the generator, preferably byvarying the field strength of the latter. In Figs. 1 and 2, we have shown this field control as accomplished by means of a variable rheostat, but the field may be otherwise varied, if desired; for example, as shown in the modification illustrated in Fig. 5, which will be described later.

As will be apparent from Fig. 2, the strength of field 16 may be varied by the rheostat 28, 29, and thatof field 23 by rheoferring to the one at the right of Fig. 1,

which controls the field of generator 4, it

comprises a suitable resistance '30 which may be gradually inserted or removed from the field circuit by means of a moving brush 31 passing over stationary contacts. The

controller for the field of generator 3 has a similar construction. The two brushes 29 and 31 are preferably joined together so as to be moved simultaneously, and we have illustrated this by the connecting bar 40. Referring to Fig. 1, which shows a typical running connectlon, the circuit to the controller may be traced from the armature of exciter 9, to the point 41, through switch 42, and by wire 43, the point 44, and from there to the stationary contact 45, through brush 31, to contact 39, through two-thirds of the resistance 30, and by wire 46 to the generator field 23, back to the point 47, through switch 48, to the other armature terminal. Moving the block 31 to the right will decrease the resistance in the circuit and therefore increase the strength of the generator field and consequently the strength of the current in the generator armature circuit. Moving the block to the left will decrease the strength of the field,

and when the block strikes contact 37 will have reduced the field to zero. A continued movement of the block toward the left will 1 first insert the entire resistance bank and successively decrease that resistance, increasing the generator armature current to its full value. The controller for the field of generator 3 is similarly constructed and arranged.

In order to control the current in the motor armature circuit when reversal takes place, we have provided suitable mechanism controlled from the generator field controllers, which is the construction we now prefer to use. C is a reversing switch for the motor circuit and may be operated, if desired, by a pair of solenoids 50, 51. With the connections as shown in Fig. 1, a branch circuit may be traced from brush 31 to stationary contact 52, to switch 53 and by wire 54, and through the solenoid 51 and back'by wires 55 and 56. This maintains solenoid 51 energized, positively holding the switch C in its position shown.

In order to brake the motor or motors when the armature connections are changed, and also to prevent a surge of current, we have preferably provided a resistance 63- through which the motor armatures may be short circuited by means of a pivoted switch 64. Referring also to Figs. 3 and 4, which, for the sake of clearness omit some of the parts, when the block 31 touches block 58, it energizes solenoid 59, raising plunger 60 from contacts 61, and ener izes solenoid 62, throwing the switch 64 rom the position shown in Fig. 1 to that shown in Flg. 3. This brakes the motor because of the short-circuit, and also inserts the resistance 63. Switch arm 64 is sufliciently wide to bridge the contacts 65, 66 before the circuit is broken. The reversing switch C is in the position shown in Fig. 3. When the block 31 has reached the position shown then shifts the switch 64 back to its be provided,

in Fig. 4 where it contacts with both blocks 58 and 67, it closes the circuit from 67, through the solenoid 50, which then throws the reversing switch to the position shown in Fig. 4, thus opening and then reversing the motor connections. As the brush 31 leaves contact 58, it deenergizes solenoid 59 allowmg its plunger to drop, and restores the connection shown in Fig. 1, through the contact points 61, and solenoid 69, which position shown in Fig. 1, cutting out the resistance 63 and restoring the circuit from the generators to the motors but with the motor connections reversed. 70 is a holding mag net to hold switch 64 until the armature current drops to the desired value, which may if desired. The other generator field controller is similarly constructed and connected. In normal running, the motor fields are kept at substantially constant excitation. When the brushes 29 and 31 are at their extreme limit of travel to the right, the fields of the generators are at full strength and the motors are running at full speed. As the brushes are shifted to the left, the generator field strength is progressively reduced substantially to zero, thus reducing the armature current and consequent speed of the motor, then the shortcircuitingresistance 63 is introduced, the motor connections changed by the reversing switch C, the generator field again built up, speeding up the motors in the reverse direction, all by a movement of the controller handle 71 in one direction.

By throwing the switches 42 and 48 to the position indicated in dotted lines, the field of the generator 4 may be thrown in parallel with the field of generator 3, both then being excited from exciter 8. Similarly, switches 14 and 19 thrown to their dotted ositions would throw the two generator elds in parallel from the exciter 9.

If switches 25 and 26 are thrown to their dotted positions, both motor fields will be energized from exciter 8. Both motor fields may be excited from exciter 9 by throwing switches 20, 22, to their dotted positions.

We prefer to provide an auxiliary prime mover, such as another combustion engine 80, driving an auxiliary exciter 81 which may be compound wound, if desired, as shown, and provided with a rheostat 82 for controlling the field strength. In order to start the engines 1 or 2, the switches 83 may be thrown to make the proper connections. If thrown on to contacts 84, the armature and field circuits of exciter 9 will be energized, driving that exciter-generator as a motor and turning over the engine 2. 'When this starts to drive, switch 83 may be opened. Throwing this switch to the dotted position will similarly drive exciter 8 as a motor to start engine 1. Of course a. compressed-air or other starting means may be used if desired. By switches 85 and 86 the fields of generators 4 and 3 may be energized from the auxiliary exciter 81, if desired.

In Fig. 5 we have shown an alternative manner of controlling the field strength of the generators 3 and 4. Only one is represented for clearness. 25' is the armature of generator 3. Instead of inserting resistance in order to reduce the field strength, this may be done by cutting out certain. of the coils of the field windings. shown this arrangement by the field coils 90 to 93 arranged in parallel, each connected to a separate block of the controller arm 31. As this arm is moved in one direction or the other from the position shown, it will successively cut out the field windings and so reduce the field strength with the same general result as the insertion of the successive resistances. This arrangement, however, has some advantages, as 1t does not waste current by the use of OllIIllC resistance.

95 represents 'an auxiliary circuit which in this case might be the ordinary shlps circuit normally supplied from the generator 81.

Although we have described the brake applied to the motor as preferably a shortcircuitin connection, it is obvious that other forms 0, brakes might be used. A compressed-air-operated. or other, friction brake applied "to the motor shaft just before the reversing switch is thrown and controlled from the present controller would accomplish some of the results which we desire, but we now consider that our present illustrated construction is preferable in this respect. We, however, do 'not desire to be limited to the brake mechanism shown and described. 7

The prime movers 1 and 2 are preferably of much greater power than. that of the auxiliary engine 80. The engines 1 and 2 are preferably of that type ofinternal combustion engines which runat a substantial 1y constant speed and in one direction only, that is to say, they are preferably non-reversing, the reversal of the electric motors being accomplished in this case without reversing the direction of movement of the prime movers or of the flow of current through the fields of the generators 3 and 4.

While we have described the-main sources of electric energy 3 and 4 as generators, and the subordinate sources 8 and'9 as exciters, it is of course evident that each one of them is a generator of electricity. In the construction illustrated, the generator 4 and its exciter 9, for example, constitute one form of a unit electric-generator mechanism.

We are aware that various modifications in the mechanism' illustrated and in the process described may be employed to ac- We have complish the advantageous results or some of the advantageous results, obtained byour preferred apparatus and method. We

, therefore do not limit the scope'of our invention to the arrangement of parts or the process herein specifically set forth.

Whatwe claim as new is:

1. In a device of the character described, a plurality of prime movers, a generator for and driven by each, electro-dynamic motor mechanism driving by said generators, common separately-exciting means for the fields of said generators and motor mechanism comprising anv exciter for and driven by each prime mover, means to vary the strengths of said generator fields, and switch mechanism arranged to deenergize the field of either generator without stop-' ping said generator or the motor mechanism.

2. In a device of the character described,

a plurality of prime movers, a generator driven by each prime mover and an exciter for that generator, dynamo electric motor mechanism whose. armature windings are supplied by said generators, a plurality of field windings on said motor mechanism adapted to be energized by said exciters, and switch mechanism arranged to connect any desired exciter to any desired one of said motor field windings.

3. In a device of the character described, a plurality of prime movers, a generator driven by each prime mover and an exciter for that generator, dynamo electric motor mechanism whose armature windings are supplied by said generators, a plurality of field windings on said motor mechanism adapted to be energized by said exciters,

a motor, or to the work circuit, as desired. 7

- 5. In a device of the character described, a dynamo electric motor, a generator supplying current to it, a brake for the motor, switch mechanism arranged to reduce the field strength of said generator and open the motor circuit, means arranged to apply said brake automatically after said field strength is so reduced and before said motor circuit is opened by said aforementioned switch mechanism, and means governed by the current in the motor armature circuit to prevent the application of said brake before said field strength is so reduced.

6. In a device of the character described, a dynamo electric motor, a generator supplying current to it, a brake for the motor, a switch arranged to open the motor circuit, a controller arranged gradually to reduce nearly to zero and then gradually" to increase the field strength of said generator, means arrangedto apply said brake automatically after said field strength is so reduced and before said motor circuit is opened by said aforementioned switch mechanism, and means governed by the current in the motor armature circuit for preventing opening of the circuit before said field strength is so reduced.

7. In a device of the character described, an auxiliary engine, an auxiliary electric generator driven thereby, a plurality of prime movers of greater power than said auxiliary engine, a generator and an exciter for that generator driven by each prime mover, and switch mechanism arranged to connect said auxiliary generator independently to either desired one of said exciters,'

whereby the latter acts as a motor to start its prime mover.

8. In a device of the character described; an auxiliary engine, an auxiliary electric generator driven thereby, a plurality of prime movers of greater power than saidauxiliary engine, a generator and an exciter for and excitin the field of that generator driven by each prime mover, and switch mechanism arranged to connect said auxiliary generator independently to either desired one of said exciters, whereby the latter acts as a motor to start its prime mover,

and switch mechanism and connections arranged to energize the fields of said generators from the auxiliary generator.

9. In a device of the character described, an auxiliary engine, an auxiliary electric generator driven thereby, a plurality of prime movers of greater power than said auxiliary engine, a generator and an exciter for that generator driven by each prime mover, and switch mechanism arranged to connect said auxiliary generator independently to either desired one of said exciters, whereby the latter acts as a motor to start its prime mover, and switch mechanism arranged to connect the fields of both generators to either exciter desired.

10. In a device of the character described, a dynamo electric motor mechanism, a plurality of independently operable motordriving units each comprising a prime mover having a generator and a generatorand-motor-field exciter driven by the primemover, controlling mechanism arranged to vary the fields of said generators simultaneously and in the same sense without varying the field of said motor mechanism, the armatures of said generators being electrically connected to each other in series and to the armature windings of said motor mechanism.

11. In a device of the character described, a dynamo electric motor mechanism, a plurality of independently operable motor-driving units each comprising a prime mover 7 having a generator and a generator-and-motor-field exciter driven by the prime-mover, controlling mechanism arranged to vary the fields of said generators simultaneously and in the same sense without varying the field of said motor mechanism, the armatures of said generators being electrically connected to each other in series and to the armatui'eivindings of said motor mechanism, and switch mechanism for each unit arranged to cut out of circuit any desired one of said units without changing the relative connections of the other unit with said motor mechanism.

12. In a device of the character described, a pair of units each comprising a generator having a field winding and an exciter therefor, motor mechanism having armature windings supplied by said generators and two field windings, switch mechanism and connections arranged to disconnect either desired exciter from its generator and connect the other exciter to the field windings of both generatorsyand switch mechanism arranged to connect either motor-field winding desired to any desired exciter.

13. In a device of the character described, a pair of units each comprising a generator having a field winding and an exciter therefor, motor mechanism having armature windings supplied by said generators and two field windings, switch mechanism and connections arranged to disconnect either desired exciter from its generator and connect the other exciter to the field windings of both generators without disturbing the connections between said generators and said motor mechanism, and switch mechanism arranged to connect either motor-field winding desire to any desired exciter.

14. In a device of the character described, a pair of units each comprising a generator having a field winding and an excitertherefor, motor mechanism having armature windings supplied by said generators in series, switch mechanism and connections arranged to disconnect either desired exciter from its generator and connect the other exciter to the field windings of both generators, and switch mechanism arranged to vary the field strengths of said generators simultaneously and in the same sense.

15. In an electric drive mechanism comprising a plurality of independently operable sources of power, each driving electric motor armature current without materiall reducing the field strength ofthe motor an when reversing said motor, reducing the said generator field strength substantially to zero without materially reducing the field strength of the motor, applying a brake to the motor and then changing the connections of the motor armature circuit.

16. In an electric drive mechanism comprising a plurality of independently operable sources of power, each driving electric generating mechanism, and a motor the armature current of which is supplied by a plurality of said generators in series,

the process of operating said drive mechanism which consists in energizing the field windings of said generator mechanismand said motor by current developed by a part of said generator mechanism other than that which supplies the motor armature circuit, controlling the operation of the motor by varying the field strength of that portion of said generator mechanism which generates the armature current, and, when reversing the motor, reducing said field strength substantially to zero, reversing the connections of the motor armature circuit and then increasing said first mentioned field strength while maintaining its former direction 0 excitation, all without materially reducing the field strength of the motor. 17. In an electric drive mechanism comprising a plurality of independent electric prising a plurality of independent electric generators, electric motor mechanism supplied by said generators in series, and a separate source of current for energizing the fields of said generators and saidmotor mechanism, the process of operating said mechanism, which consists in energizing in parallel from said se arate source a field winding of one of sai generators and a field winding of said motor mechanism and similarly energizing the field winding of another generator and another portion of tions t an? the field of said motor mechanism, and controlling said motor by simultaneously varying the excitation of the fields of said generators without materially varying the strength of the motor field.

19. In apparatus of the class described, a plurality of independently operable prime movers, a generator for and driven by each prime mover, dynamo-electric motor mechanism c'omprising a plurality of fields and a plurality of armatures, electrical connections between the armatures of said generators in series and the armatures of said motor mechanism comprising controlling mechanism whereby the armatures of any or all of said generators may be operatively connected to any or all of the armatures of said motor mechanism, and means for simultaneously varying the field excitation of said generators, including reduction of said excitation to zero, without substantially varying the field excitation of said motor mechanism.

20.1n apparatus or" the class described, a plurality of independently operable prime movers, a generator for and driven by each prime mover, dynamo-electric motor mechanism comprising a plurality of fields and a plurality of armatures, electrical connecincluding controlling mechanism whereby the armatures of said generators and the armatures of said motor mechanism may all be connected in series or any or tially varying the field excitation of said motor mechanism.

21. In an electric drive mechanism comprising a plurality of sources of power, electric generating mechanism driven from each source of power, electric motor mechanism receiving its armature current from said generators in series, and means for exciting the fields of said generator mechanism and said motor mechanism, the process of efiecting the reversal of said electric drive mechanism when connected to a part to be driven of considerable inertia, without interrupting the connection, which consists in maintaining the motor field substantially constant, reducing the armature current substantially to zero, opening said armature circuit, reversing the circuit connections and gradually bringing the armature current again up to normal.

22. In an electric drive mechanism comprising a plurality of sources of power, electric generators driven therefrom, an electric motor receiving its armature current from said generators in series, and means for exciting the fields of said generators and said it'upagain to normal.

motor, the process of efiecting the-reversal of such mechanism when connected to' a part to be driven of considerable inertia, without interrupting the connection, which;

consists in maintaining the motor field subarmature current-and gradually bringing 23. In an electric drive mechanism comprising a plurality of sources of power,

electric generators driven therefrom, an

electric motor receiving its armature current from said generators in series, and means for exciting the fields of said generators and said motor,the process of effect: ing the reversal of such mechanism when connected to a part-to be driven of consid: erable inertia, without the interruption of the connection, which consists in maintaining the motor field substantially constant, reducing the motor armature current by re:

ducing the field strength of the generators until the armature current is brought sub-v stantially to zero, then reversin the direction of the armature current an gradually restoring said generator field to build said armature current again up to normal.

- 24. In an electric drive mechanism for propelling ships, the combination with a plurality of primemovers of substantially equal capacity, agenerator for and driven by each prime mover, electric motor mechanism with which said generators are connected in series, a plurality of exciters con-- nected to and driven from said prime movers, and switch mechanism by which any exciter may be connected to the field of any prime mover and to any field of said motor mechanism.

25. In an electric drive mechanism, for

propelling ships, the combination with a plurality of prime movers of substantially equal capacity, a generator for and driven by each prime mover, electric motor mechanism with which said generators are connected in series, a plurality of exciters connected to and driven from said prime movers, and switch mechanism by which the exciter connected to anyprime mover may be connected'to the fields of any combination of generators, or to any combination of motor fields, or to both.

26. In an electric drive mechanism, the combination with a source of power, electric generating mechanism driven therefrom, an electric motor mechanism receiving its armature current from said generating mechanism, and exciting means supplying the fields of said generating mechanism and said motor mechanism, of means for effect- I ing the-reversal of said motor mechanism when connected to a part to be driven, without interrupting said connection, comprising a controller switch operating upon a continuous movement to reduce the field strength of said generating mechanism and correspondingly. the armature current substantially tozer'o-and then again to build it up to normal, means electrically controlled from said switch for automatically reversing the armature current and for opening the armature circuit before the armature current is reversed, and means in the armaturecircuit and governed by the current flow therein for holdin the circuit opening meansinoperative unti the current insaid armature circuit. ,l i reduced to a predetermined point; a

27. In an. electric drive mechanis" combination with a [source of power,

generating mechanism driven therefrom, an I electric motor mechanism receiving" fits armature current from said generating mechanism, and exciting means supplying the fields of said generating mechanism "and said motor mechanism, of means. for eflecting a reversal of said motor mechanism, comprising a controller switch for reducing the field excitation of the enerating mechanism to effect a corresponding reduction of themotor armature'current, means electrically connected to said controller switch for automatically reversin the motor armature circuit, means also e ectrically connected to said controller switch and arranged to be energized before the energiza tion of said reversing means to open said armature circuit, and means governed by the flow of current in the armature circuit for last-mentioned means.

28. In an electric drive mechanism, the

combination with a source of power, electric generating mechanism driven therefrom and electric motor mechanism receiving itsarmature current from said generating mechanism, of means for efi'ecting a reversal of said motor mechanism when connected to a part to be driven without interru ting said connection, comprising a control er switch for efl'ecting a gradual reduction of the motor armature current, means electrically connected to said controller switch for automatically reversing said motor armature circuit, means also electrically connected to said controller switch and arranged to be energized before said reversing means for automatically opening said armature circuit and short-circuiting said armature through resistance, and means controlled by the armature current for preventing the operation of said last-mentioned means until the armagure current is reduced to a predetermined ow. 29. In an electric drive mechanism for propelling ships, the combination with a plurality of prime movers, a generator for and driven by each prime mover, electric motor mechanism receiving its armature cur rent from said generating mechanism, said generators being connected in series, means for exciting the fields of said generators and said motor mechanism, and means for re-; versing the motor mechanism comprising means for simultaneously and gradually reducing the field excitation of said genera- ,tors while maintaining substantially constant the field excitation of said motor mechanism, and means associated -withsaid reducing means and operating at the end of the reducmg movement of said means for short- -circuiting the motor mechanism through resistance to brake the movement thereof, and

means for reversing the motor armature circuit, said last mentioned three means being electrically interlocked to insure their operation-in a predetermined sequence.

30. In an electric drive mechanism for the motor mechanism comprising means arranged to reduce the excitation of the generator fields while maintaining substantially constant the field excitation of the inotor mechanism, means for preventing reversal until the armature current has been reduced to a predetermined point, means for shortcircuiting the motor armature through resistance, and means for then reversing the circuitconnections.

31. In an electric drivemechanisin, they combination with a source of power, dynamo electric generating mechanism, dynamo electric motor mechanism receiving its armature current from said generating mechanism, exciting means for the fields of said mechanism, and means for reversing the motor mechanism comprisin a controller switch arranged to reduce t e field excitation of the generatin mechanism while maintaining substantia ly constant field excitation of the motor mechanism, means electrically connected to said controller switch for automatically reversing the circuit supplying the armature current at a predetermined point in the movement of said switch, means also electrically connected to said controller.

switch and timed to operate before said reversing means to short-circuit the armature throughresistance, and means controlled by the current flow in the circuit supplying armature current for preventing the operation of said short-circuiting means until said current flow has been reduced to a predetermined point. v

A Signed at Port. Chester, New York, this 26th day of August 1919. 1

HARRY SHOEMAKER. CLIFFORD D. MALLORY.

Bil 

